parisc: add parisc code patching

Instead of re-mapping the whole kernel text with RWX rights
add a patch_text() which can be used to replace instructions
in the kernel .text section. Based on the ARM implementation.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/arch/parisc/include/asm/patch.h b/arch/parisc/include/asm/patch.h
new file mode 100644 (file)
index 0000000..685b58a
--- /dev/null
+++ b/arch/parisc/include/asm/patch.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _PARISC_KERNEL_PATCH_H
+#define _PARISC_KERNEL_PATCH_H
+
+/* stop machine and patch kernel text */
+void patch_text(void *addr, unsigned int insn);
+
+/* patch kernel text with machine already stopped (e.g. in kgdb) */
+void __patch_text(void *addr, unsigned int insn);
+
+#endif

diff --git a/arch/parisc/kernel/Makefile b/arch/parisc/kernel/Makefile
index 8e5f1ab65c68d493198c55937639de24e21fa7d2..d29bbd1a73b25e1437f5fd460f8420b4709248b9 100644 (file)
--- a/arch/parisc/kernel/Makefile
+++ b/arch/parisc/kernel/Makefile
@@ -9,7 +9,8 @@ obj-y           := cache.o pacache.o setup.o pdt.o traps.o time.o irq.o \
                   pa7300lc.o syscall.o entry.o sys_parisc.o firmware.o \
                   ptrace.o hardware.o inventory.o drivers.o alternative.o \
                   signal.o hpmc.o real2.o parisc_ksyms.o unaligned.o \
-                  process.o processor.o pdc_cons.o pdc_chassis.o unwind.o
+                  process.o processor.o pdc_cons.o pdc_chassis.o unwind.o \
+                  patch.o
 
 ifdef CONFIG_FUNCTION_TRACER
 # Do not profile debug and lowlevel utilities

diff --git a/arch/parisc/kernel/patch.c b/arch/parisc/kernel/patch.c
new file mode 100644 (file)
index 0000000..8c5ee68
--- /dev/null
+++ b/arch/parisc/kernel/patch.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+ /*
+  * functions to patch RO kernel text during runtime
+  *
+  * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
+  */
+
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/kprobes.h>
+#include <linux/mm.h>
+#include <linux/stop_machine.h>
+
+#include <asm/cacheflush.h>
+#include <asm/fixmap.h>
+#include <asm/patch.h>
+
+struct patch {
+       void *addr;
+       unsigned int insn;
+};
+
+static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
+{
+       unsigned long uintaddr = (uintptr_t) addr;
+       bool module = !core_kernel_text(uintaddr);
+       struct page *page;
+
+       if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
+               page = vmalloc_to_page(addr);
+       else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
+               page = virt_to_page(addr);
+       else
+               return addr;
+
+       set_fixmap(fixmap, page_to_phys(page));
+
+       return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
+}
+
+static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
+{
+       clear_fixmap(fixmap);
+}
+
+void __kprobes __patch_text(void *addr, unsigned int insn)
+{
+       unsigned long flags;
+       void *waddr = addr;
+       int size;
+
+       waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);
+       *(u32 *)waddr = insn;
+       size = sizeof(u32);
+       flush_kernel_vmap_range(waddr, size);
+       patch_unmap(FIX_TEXT_POKE0, &flags);
+       flush_icache_range((uintptr_t)(addr),
+                          (uintptr_t)(addr) + size);
+}
+
+static int __kprobes patch_text_stop_machine(void *data)
+{
+       struct patch *patch = data;
+
+       __patch_text(patch->addr, patch->insn);
+
+       return 0;
+}
+
+void __kprobes patch_text(void *addr, unsigned int insn)
+{
+       struct patch patch = {
+               .addr = addr,
+               .insn = insn,
+       };
+
+       stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
+}